Structure and Phase Transition in (C

Structure and Phase Transition in (C

H

NH

)

Sb

Cl

·(C

H

NH

)SbCl

; X-ray, DSC and Dielectric Studies

Maciej Bujak and Jacek Zaleski

Institute of Chemistry, University of Opole, Oleska 48, 45 052 Opole, Poland Reprint requests to Prof. J. Z.; Fax: ++48 77 4410741; E-mail: zaleski@uni.opole.pl Z. Naturforsch. 55 a, 526–532 (2000); received January 10, 2000

The structure of (C2H5NH3)3Sb2Cl9 (C2H5NH3)SbCl4 at 295 K has been determined. The crystals are orthorhombic, space group Pna21(a = 16.925(3), b = 24.703(5), c = 7.956(2) ˚A, V = 3326.4(12) ˚A³, Z = 4, dc= 2.018, dm = 2.01(1) Mg m ³). They consist of an anionic sublattice composed of two different polymeric zig-zag chains. One is built of Sb2Cl9

3 units (corner sharing octahedra) and the other one is made of corner sharing SbCl5

2 square pyramids. In the cavites between the polyanionic chains four non-equivalent ethylammonium cations are located. Three of them are disordered. The cations are connected to the anions by weak N-H...Cl hydrogen bonds. A first order phase transition of the order-disorder type was found at 274 K. It was studied by DSC, dielectric and X-ray diffraction methods. The mechanism of the phase transition is attributed to the ordering of at least one of the ethylammonium cations.

Key words: Ethylamine; Chloroantimonate(III); Structure; Phase Transition.